Most of the natural bio-active molecules are chiral. Examples to illustrate this and highlight the differences in bio-activity.

1. Valliappan Kannappan
Valliappan Kannappan
VALLIAPPAN K
Professor of Quality Assurance (Retd.)
Department of Pharmacy
Annamalai University
INDIA
2021
Chirality in NPs
15 min.

2. Valliappan Kannappan
Valliappan Kannappan
Ascorbic acid
Ascorbic acid
Quinidine
Quinidine
N
A
T
U
R
A
L
O
R
I
Chiral Bio
Chiral Bio-
-active molecules
active molecules
2021
Chirality in NPs
(-)-Hyoscamine
(-)-Hyoscamine
Fungicides
I
G
I
N

3. Valliappan Kannappan
Valliappan Kannappan
F
F
R
R
A
A
G
G
R
R
A
A
N
N
C
C
E
E
S
S
(S) Limonene  (R)
Lemon odor Orange odor
2021
Chirality in NPs
caraway spearmint
(S) Caravone  (R)

4. Valliappan Kannappan
Valliappan Kannappan
F
F
L
L
A
A
V
V
O
O
R
R
S
S
(S)  Asparagine  (R)
bitter sweet
NH2
(R)
HO
O
O
NH2
H
H2N (S)
OH
O
O
H2N H
2021
Chirality in NPs
sweet bitter
(S, S)  Aspartame  (R, R)
(S)
N
H
(S)
O
O
HO
O
O
NH2
H
H

5. Valliappan Kannappan
Valliappan Kannappan
F
F
U
U
N
N
G
G
I
I
C
C
I
I
D
D
E
E
(S)  Metalochlor  (R)
inactive
2021
Chirality in NPs
(R)-enantiomer is 1000x more active in vitro than (S) -isomer
(S)  Metaxylyl  (R) N
(R)
CH3
O
O
O
O
H
N
(S)
H3C
O
O
O O
H


6. Valliappan Kannappan
Valliappan Kannappan
fungicide Plant growth regulator
N
N N
(S) (S)
CH3
CH3
CH3
OH
H
H
Cl
F
F
U
U
N
N
G
G
I
I
C
C
I
I
D
D
E
E
2021
Chirality in NPs
(2R,3R) Paclobutrazol (2S,3S)
The chiral twins of Paclobutrazol exhibit wildly differing biological
activities

7. Valliappan Kannappan
Valliappan Kannappan
H
E
R
B
C
I
D
E
(R)-Mecoprop;
Herbicidal activity (inhibition of the activity of the plant growth hormone, indole-
3-acetic acid) resides virtually in the R-enantiomer
eutomer
2021
Chirality in NPs
N
H
O
(R)
NHC2H5
O
O H CH3
(R)-Carbetamide; eutomer;
developed as pure enantiomer

8. Valliappan Kannappan
Valliappan Kannappan
( S,2R,3R)- Deltamethrin

3 2
I
I
N
N
S
S
E
E
C
C
T
T
C
C
I
I
D
D
E
E
2021
Chirality in NPs
Deltamethrin is Pyrethroid insecticide; Chemically an
ester of m-phenoxybenzaldehyde cyanohydrin; has three
stereogenic centers and is sold as an enantiopure molecule with
configuration (S,R,R).

9. Valliappan Kannappan
Valliappan Kannappan
(-)-Morphine
O
O
L
L
D
D
C
C
D
D
2021
Chirality in NPs
 Millennia-old-unichiral drug is the opioid agent morphine;
Opium powder is the dried juice from the unripe seed capsule of
the poppy Papaver somniferum; analgesic and euphoric;
 Pentacyclic 3amine (alkaloid) with 5 stereogenic centers (25 = 32
stereoisomers) and the natural product is the (-)-enantiomer –
analgesic activity
(-)-Morphine

10. Valliappan Kannappan
Valliappan Kannappan
(+)-Ascorbic acid
2021
Chirality in NPs
(+)-Ascorbic acid
 (+)- Ascorbic acid exhibits the redox activity, where as
the (-)- enantiomer is inactive and cannot be used to
treat scurvy

11. Valliappan Kannappan
Valliappan Kannappan
The herb Ephedra sinica contains ephedrine and Pseudo-ephedrine
Sympathomimetic amine
(alkaloid); CNS Stimulant, , treat
hypotension, Bronchodilator,
appetite suppressant
(1R,2S)-2-(methylamino)-1-phenyl-
propan-1-ol
(-)-1R,2S-Ephedrine
O
O
L
L
D
D
C
C
D
D
2021
Chirality in NPs
The herb Ephedra sinica contains ephedrine and Pseudo-ephedrine
as its principle active ingredients;
Ephedrine has two stereogenic centers, exhibits enantiomerism
and is unichiral ; (1R,2S)- and (1S,2R)-enantiomers are designated
ephedrine, (1R,2R)- and (1S,2S)-enantiomers as pseudoephedrine
In April 2004, USFDA banned the sale of ephedrine and dietary
supplements containing ephedrine due to serious adverse effects

12. Valliappan Kannappan
Valliappan Kannappan
Antimalarial activity
(-)-Quinine
2021
Chirality in NPs
Antimalarial activity
 Most fascinating old chiral drug, from historical point of view is
Quinine (1600s); Bark of Cinchona tree;
 Contains two major fused ring systems: aromatic quinoline
and bicyclic quiniclidine
 Stereoselective synthesis of quinine was successfully done in 2001,
181 years after compound was first isolated

13. Valliappan Kannappan
Valliappan Kannappan
(-)-Quinidine
(S)
(R)
O
HO
N
(S)
(R)
H
(R)
(S)
O
HO
N
(S)
(R)
H
(-)-Quinine
2021
Chirality in NPs
Quinidine is a diastereomer of Quinine and is employed as an
antiarrythmic agent; Stereoisomeric alkaloids exhibiting different
therapeutic effects
N N
antimalarial
Antiarrythmic

14. Valliappan Kannappan
Valliappan Kannappan
(-)-Cocaine The Coca Plant;
Erythroxylon coca
2021
Chirality in NPs
(-)-Cocaine
 Cocaine is a tropane alkaloid obtained form the leaves of coca
plant; employed topical anesthetic in eye and nasal surgery,
although it is now predominantly used for nasal and lachrymal
surgery.
 (-)-cocaine was found have 50 x more affinity than its enantiomer
Erythroxylon coca

15. Valliappan Kannappan
Valliappan Kannappan
N
O OH
H3C
O
Stereochemically atropine
is an interesting case; This
racemic substance is
believed not to occur in
naturally
2021
Chirality in NPs
(-)-Hyosciamine
 (-)-Hyoscyamine occurs in several Solanaceae plant species
and is racemized to atropine during isolation
 (S)-(-)-Hyoscyamine was found to be 12-20 X more potent
than the (+)-enantiomer in a variety of pharmacological effects
viz. mydriasis, salivary secretion , etc.

16. Valliappan Kannappan
Valliappan Kannappan
Thanks for
Thanks for your
your time
time
2021
Chirality in NPs
valliappan
valliappan
Chirally Yours
Chirally Yours